Effect of Shot Peening-Induced Microstructure and Precipitate Evolutions on the Surface Residual Stresses, Hardness, and Wear Behavior of Al 6061 Alloy
摘要
Shot peening has proven to be an effective surface treatment for enhancing the hardness and wear resistance of Al 6061 alloy by inducing significant microstructural refinement and compressive residual stresses. This study explores the impact of shot peening on the grain structure, surface morphology, precipitation behavior, hardness, and wear resistance of Al 6061. Microstructural analysis revealed notable grain refinement, with the mean grain size reduced from 95 microns to 8.2 microns and precipitate size reduced from 1.5 microns to approximately 1 micron. These modifications, coupled with a compact, plastically deformed surface layer, resulted in a significant increase in hardness, reaching 111.1 HV near the surface, and improved wear resistance. EDS analysis demonstrated a more uniform distribution of Mg₂Si precipitates and the presence of a thin oxide layer, contributing to enhanced hardness. The introduction of compressive residual stresses, measured at − 335 MPa at a depth of 300 microns, further strengthened the alloy by preventing crack initiation and propagation. Wear test results indicated a reduction in wear rate from 8.1 to 4.2 mg/m × 103 under a 25 N load and a decrease in the coefficient of friction (COF) from 1.13 to 0.98, attributed to the refined microstructure, increased surface hardness, and compressive stress profile.